1. The Field of the Invention
The present invention relates to vehicle airbag systems. More specifically, the invention relates to an array of nozzles integrated with an inflator housing for even distribution of exhaust gas generated by the inflator.
2. Technical Background
Inflatable airbags are well accepted for use in motor vehicles and have been credited with preventing numerous deaths and injuries. Some statistics estimate that frontal airbags reduce the fatalities in head-on collisions by 25% among drivers using seat belts and by more than 30% among unbelted drivers. Statistics further suggest that with a combination of seat belt and airbag, serious chest injuries in frontal collisions can be reduced by 65% and serious head injuries by up to 75%. Airbag use presents clear benefits. Airbags are generally required in most all new vehicles.
A modern airbag apparatus may include an electronic control unit (ECU) and one or more airbag modules. The ECU includes a sensor which continuously monitors the acceleration and deceleration of the vehicle and sends this information to a processor which processes an algorithm to determine if the vehicle is in an accident situation.
When the processor determines that there is an accident situation, the ECU transmits an electrical current to an initiator in the airbag module. The initiator triggers operation of an inflator or gas generator which, in some embodiments, uses liquefied gas, compressed gas, solid fuel, and/or their combination. The inflator inflates a textile airbag that cushions a passenger during impacts to prevent injury to the passenger. In some airbag apparatuses, the airbag may be fully inflated within 50 thousandths of a second and deflated within two tenths of a second.
Airbag technology has advanced to include airbag apparatuses which protect occupants during a side impact, or roll-over accident. In these accidents, the occupant may be thrown against the windows, doors and side-walls of the vehicle. These airbag apparatuses are known as curtain airbags. Generally, the curtain airbag is attached to a thin long frame member which runs along a side of the roof of the vehicle. Often due to window size and visibility requirements, the curtain airbag apparatus, including the inflator are of a long thin shape. Other airbags inflate to position knee bolsters to keep an occupant within the vehicle and in an optimal position for other airbags to protect the occupant.
While many advances have been made in the textile bags used, as well as accident detection sensors, little has changed with regard to the airbag inflators. Generally, to provide sufficient inflation gas within the required short time period initiators connected to the inflators activate a gas generant. The gas generant may include compressed gas, liquefied gas, solid fuel, or a combination of these. Generally, the inflation gas is created from the rapid burning of pyrotechnic materials. The gas (also referred to herein as exhaust gas) escapes exit ports in the inflator at a high velocity and temperature.
Conventionally, the inflator includes one or two exit ports formed in the inflator housing. The exit ports are sized to ensure that sufficient exhaust gas escapes the inflator housing at an appropriate velocity to quickly fill the airbag. Generally, due to the velocity of the exhaust gas, the airbag inflates almost spherically from the location of the one or two exit ports.
Spherical inflation of the airbag may be problematic depending on the shape of the airbag. For example, with a driver's side airbag, which is generally spherical in shape, spherical inflation may not be a problem. However, in a curtain airbag, spherical inflation, or inflation from a single point source, may cause several problems including bag slap (referring to the un-inflated portion of an airbag striking an occupant while inflating). Spherical inflation may cause delayed inflation of certain airbag portions, and/or pre-stress portions of the airbag in the vicinity of the point inflation source such that the pre-stressed portions fail during operation of the airbag.
Regardless of the shape of the airbag, the airbag is preferably inflated very quickly and in a uniform manner. To overcome problems caused by spherical inflation, conventional inflators include a diffuser. A diffuser may be used to direct and diffuse the exhaust gas. The diffuser may be secured to the inflator and include a plurality of holes to allow the exhaust gas to be distributed over a larger surface area compared to a point inflation source.
Diffusers provide more uniform inflation of the airbag. However, using a diffuser impedes the flow of exhaust gas. Thus, more gas generant may be required to maintain the needed exhaust gas flow velocity. In addition, because diffusers are generally separate components, production, assembly and material costs for the airbag may be increased. In addition, with an additional part, the diffuser, the potential for defective parts, and/or assembly errors increases.
In addition, the holes of the diffuser are generally of a single size, and uniform shape. The holes generally do not accelerate the exhaust gas. Typically, the holes decelerate the exhaust gas. If exhaust gas velocity were increased, less gas generant may be required.
Furthermore, vehicle manufacturers are required to provide operable airbags for the expected life of a vehicle, which may be as long as ten to twenty years. Over the life of a vehicle, the inflator may be exposed to various temperatures and climates. This exposure may cause interference with the exit ports and/or diffuser holes. For example, condensation within the inflator may cause the gas generant to break up or become neutralized.
In addition, because most conventional inflators are limited to spherical inflation, certain limitations are imposed on how the airbag modules are packaged and where airbag modules are located within a vehicle. For example, due to space requirements and spherical inflation, airbag modules are generally not located in a door side panel. Instead, a side-impact airbag module may be located in a side of an occupant's seat. The airbag module may designed to accommodate spherical inflation by inflating forward to position an airbag between an occupant and the door. The airbag module may rely on an occupant being “in position” (occupants who are buckled, or riding in an anticipated position) during an accident. However, if an airbag module could inflate in two-dimensions from the door, more effective protection of an occupant may be provided. In addition, such an airbag could better protect occupants who may be out-of-position.
Accordingly, it would be an advancement in the art to provide an airbag inflator that has an inflatable surface including a plurality of nozzles. It would be a further advancement to provide an airbag inflator which allows the velocity of the exhaust gas to be controlled through the use of nozzles. Additionally, it would be an advancement in the art to provide an airbag inflator which is hermetically sealed from external elements. It would be another advancement in the art to provide an airbag inflator which allows for selective flow of exhaust gas through the plurality of nozzles. A further advancement in the art would be to provide an airbag inflator which includes fewer parts, reduces production costs, and reduces potential for defective parts and/or design flaws.